Docker + SkyDNS + Upstart

etc-default-docker

# Docker Upstart and SysVinit configuration file

# Customize location of Docker binary (especially for development testing).
#DOCKER="/usr/local/bin/docker"

# Use DOCKER_OPTS to modify the daemon startup options.
DOCKER_OPTS="-r=false --dns 172.17.42.1 --dns 8.8.8.8 --dns 8.8.4.4"

# If you need Docker to use an HTTP proxy, it can also be specified here.
#export http_proxy="http://127.0.0.1:3128/"

# This is also a handy place to tweak where Docker's temporary files go.
#export TMPDIR="/mnt/bigdrive/docker-tmp"

etc-init-docker.conf

description "Docker daemon"

start on filesystem
stop on runlevel [!2345]
limit nofile 524288 1048576
limit nproc 524288 1048576

respawn

pre-start script
	# see also https://github.com/tianon/cgroupfs-mount/blob/master/cgroupfs-mount
	if grep -v '^#' /etc/fstab | grep -q cgroup \
		|| [ ! -e /proc/cgroups ] \
		|| [ ! -d /sys/fs/cgroup ]; then
		exit 0
	fi
	if ! mountpoint -q /sys/fs/cgroup; then
		mount -t tmpfs -o uid=0,gid=0,mode=0755 cgroup /sys/fs/cgroup
	fi
	(
		cd /sys/fs/cgroup
		for sys in $(awk '!/^#/ { if ($4 == 1) print $1 }' /proc/cgroups); do
			mkdir -p $sys
			if ! mountpoint -q $sys; then
				if ! mount -n -t cgroup -o $sys cgroup $sys; then
					rmdir $sys || true
				fi
			fi
		done
	)
end script

script
	# modify these in /etc/default/$UPSTART_JOB (/etc/default/docker)
	DOCKER=/usr/bin/$UPSTART_JOB
	DOCKER_OPTS=
	if [ -f /etc/default/$UPSTART_JOB ]; then
		. /etc/default/$UPSTART_JOB
	fi
	exec "$DOCKER" -d $DOCKER_OPTS
end script

post-start script
	# Emit custom event to initialize Skydock DNS
	echo "Docker spawned"
	exec initctl emit docker-spawned
end script

etc-init-skydns.conf

description "Start docker dns service. See: https://github.com/crosbymichael/skydock"
author		"Tadeusz Łazurski"

start on starting docker-skydock

respawn 
console log

script 
	echo "Starting skydns container"
	exec docker start -a skydns
end script

post-start script
	# Try to query our DNS service 20 times with 1s timeout.
	# Consider our service to be running when we get any response.
	dig @172.17.42.1 +short +time=1 +tries=20 '*'
end script	

etc-init-skydock.conf

description "Start skydock service. See: https://github.com/crosbymichael/skydock"
author		"Tadeusz Łazurski"

start on docker-spawned # Custom event. See docker.conf post-start script.

respawn
console log

script
	echo "Starting skydock container"
	exec docker start -a skydock
end script

post-start script
	# Delay `started` event.
	# Is there a better way to ensure skydock is initialized before starting other containers?
	sleep 2
end script